ccpr: Add a GrOctoBounds class

Encapsulates all the various code dealing with 45-degree bounding
boxes into a central GrOctoBounds class.

Bug: skia:
Change-Id: Ibc8ac4371af8f310e711579c3c77e0b3a53aff0f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/212563
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
9 files changed